Published online: August 16, 2020
Eosinophils make up about 1~3% of white blood cells in healthy individuals and act as a component of the immune system responsible for allergy. In patients with asthma, an inverse association between lung function (measured as forced expiratory volume in 1 s; FEV1) decline and blood eosinophil counts (BECs) was reported. This association may be related with tissue damage and inflammation caused by eosinophils. However, little has been known about the long-term effects of consistently elevated BECs on lung function decline in healthy individuals.
In a recent study published in The Journal of Allergy and Clinical Immunology: In Practice, Lee and colleagues assessed the associations between BEC and decline in FEV1 using a well-established health screening database. This database included 4,634 healthy individuals and the mean number of health-screenings was 7.5 over an average of 11.7 years of observation. In subpopulation analyses, they classified participants into 4 groups according to their stability of BECs to reflect the BEC consistency: all measurements < 100/μL, > 100/μL, > 200/μL, and > 300/μL.
A higher BEC was significantly associated with greater FEV1 decline that was stronger in non-smokers than in smokers. In subpopulation analyses of 2018 individuals with consistent BECs, those with BECs consistently > 100/μL (FEV1 decline mean; -38.6 mL/year), > 200/μL (FEV1 decline mean; -41.6 mL/year), and 300/μL (FEV1 decline mean; -46.7 mL/year) had a significantly higher, dose-dependent FEV1 decline than those with BECs consistently < 100/μL (FEV1 decline mean; -34.5 mL/year). A BEC threshold of 100/μL in non-smokers and 200/μL in smokers may predict accelerated FEV1 decline.
BEC is associated with a decline in FEV1, and a consistently high BEC is an independent risk factor for accelerated FEV1 decline in healthy individuals. These results suggest the use of the BEC to identify healthy individuals at high risk for developing chronic lung disease, which in turn may enable a tailored preventive strategy.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.